<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=1, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
    *{margin:0;padding: 0}
    input,button{
        width:200px;
        height:30px;
        border: 1px solid #333;
        padding:5px;
    }
    button{
        box-sizing:content-box;
    }
    /* button默认 box-sizing:border-box 给边框和填充不会改变它的width,height*/
    </style>
</head>
<body>
    <input type="text"><br>
    <button>btn</button>
</body>
</html>